1. Field of the Invention
This invention relates to an automated method and apparatus for the collection and processing of environmental samples from a plurality of collection sites. In particular, the invention is a system for monitoring time sensitive environmental parameters at collection sites, such as monitoring radiation levels in a nuclear facility. Distributed sample holders are encoded by optically readable identity labels which are read using a portable scanner or image collection unit upon deployment and collection of the sample holder and upon analysis of the sample. The portable unit automatically indexes the identity code to the time at which the identity code is scanned. The site is also encoded and information respecting certain parameters at the collection site can be encoded and/or compared to stored nominal standards. The data thus collected are downloaded to a processor, for generating an error-free report of the status and trends of the radiation levels at distributed locations, and for monitoring the collection of data in an accountable manner.
2. Prior Art
Certain forms of environmental testing procedures employ sample collectors which are deployed at particular locations to be monitored, and left in place over a period of time. During this time, environmental factors produce changes in the sample collector. By collecting the sample collectors and analyzing their condition it is possible to assess the ambient levels of these environmental factors at the location where the sample collector was deployed. Various environmental factors can be monitored in this way.
One form of relatively demanding environmental monitoring involves testing ambient radiation levels, although the invention is also applicable to monitoring other parameters. It may be desirable to monitor radiation levels in a nuclear power generation plant, in a production or handling facility for nuclear fuel, in weapons facilities, in radiological facilities, etc. It may also be desirable to monitor radiation levels on a more domestic level, for example to detect concentrations of radon.
Ionizing radiation can be sensed using a material which is physically altered by subatomic particles passing through the material, leaving tracks which can be counted. The number of tracks is a function of the radiation level and the time of exposure of the material. Radiation levels can also be detected by accumulating airborne dust in a sample collector, e.g., using a filter and a powered airflow means. The dust can include particles of radioactive isotopes, or for example in the case of radon, the chemical or radioactive decay products which result. These chemical and/or radioactive species are accumulated, trapped or adsorbed, for example being trapped in a filter arrangement coupled to a suction inlet having a known flow rate, or simply deposited on surfaces of material such as charcoal in the sample collector, for quantitative testing.
By detecting radiation emitted from the sample by radioactive decay of isotopes captured by the sample collector, for example by determining the rate of alpha emissions, it is possible to obtain an indirect measure of the concentration of radioactive isotopes at the site of collection. The radioactivity of the material collected is partly a function of the concentration of the radioactive isotope at the testing site and partly a function of the length of time the sample collector was deployed. Similarly, the amount of a chemical species accumulated in this manner can be determined as a measure of the concentration of the chemical species, or of the concentration of a predecessor species in a known reaction.
In measuring concentrations of radioactive materials from radioactive emissions of a collected sample, the half life of radioactive isotopes of interest affects the relationship between the level of radiation during exposure of the sample and the level of radiation emitted by the sample during later testing. The manner in which the sample was collected, such as the extent of air flow through a filter, also affects the amount of material collected. To obtain an accurate measurement for isotopes which have a half life that is relatively short compared to the sampling interval or compared to the delay between recovery of the sample collector and analysis, it may be necessary to compute backwards, with knowledge of the half life of the isotope and the manner of its collection, in order to assess the ambient concentration of the isotope over the period that the sample was taken. It is sometimes necessary to analyze the sample twice, in order to calculate the respective concentrations of isotopes having different half lives, for example testing the sample shortly after recovery of the sample holder, and again after several days.
Typically, samples are collected repeatedly in an ongoing monitoring process. A technician recovers each of the sample collectors, installs a fresh sample collector, and after collecting a group of sample collectors delivers them for testing to analyze their contents. Whereas the accuracy of measurement is critically related to the times of deployment, collection and testing of the sample collector, and in the case of a filter to the volume of air passing through the filter, accuracy of data collection is very important. A large number of sample collectors may be needed to monitor a large number of sites in and around a plant. For these reasons the problem of managing an environmental monitoring system can be formidable.
Sample collectors can be labelled with identity information such as serial numbers or can be kept in packaging materials which are labeled as to collector identity or collection site. At each of the steps (deployment, collection and testing), the time must be recorded and indexed to the particular sample collector. At least once during the process, information identifying the site of deployment must also be recorded to enable the data to be reported as to the specific collection site, and the manner of exposure of the sample collector must be noted. It is then necessary after collecting and analyzing all these data to sort out useful information such as the conditions and trends at the particular sites or at groups of sites having some relationship (e.g., proximity to a potential source of radiation leakage).
It is unavoidable that errors will occur in the collection of all this data. Typically, the name or other identity code of the technician installing, collecting and/or testing the sample is recorded to help track any samples which become lost or otherwise to resolve errors which may occur. This information is also useful for general management information purposes.
Early identification of a problem resulting in an increase in radiation level at a plant site is important to ensure the health of workers, and also to enable a rapid response to equipment failure, should that be the underlying cause of the change in radiation level. It would be desirable to improve the process of data collection in a way that reduces the potential for errors. It would also be desirable to improve data collection in a way that leads smoothly into the process of analyzing the data to identify trends in the data, to cross correlate occurrences on the premises with effects in the detected concentrations, and similarly to accurately gather, and make as much practical use as possible, of the information potentially available.
The present invention ensures accuracy and completeness of data gathering without the need to record sample collector codes, site codes or times manually. This is accomplished by providing a portable apparatus having an on-board processor and optical reader, which automatically stores the time when recording a sample collector code or site code to be referenced to the sample collector. The portable data collector can also input data respecting collection parameters, entered either manually on a keyboard or by automatic means operable to record an optical image of a meter face or the like. The portable data entry unit compares this parameter data with maximum and minimum expected levels of the parameters, stored to define a profile of the respective collection site, enabling corrective action when out-of-range data is presented. The portable apparatus is coupleable in data communication with a computer workstation operable to upload the data from the portable apparatus, and to associate test results from analysis of the contents of the sample collector with the site, the time, and the conditions, and also to monitor the location and chain of custody of sample collectors through the process. In this manner, errors in data collection are substantially reduced and the collected data is available in a manner facilitating automatic processing steps such as statistical and trend analyses, prompt reporting of problems, graphic presentation of the data and management information for improving the efficiency of the process as a whole.